PXF4336 Datasheet, PDF (85/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
Bandwidth not reserved
10
9
8
10
7
9
8
7
6
6
5
4
3
2
1
1
9
7
6
scheduler
output rate
1
real-time
traffic
connection setup
with guaranteed
cell rates
not reserved
b a n d w id th
d ist rib u t e d
unused
b a n d w id th
d is tr ib u te d
Figure 3-25 Scheduler Behavior Example
The three columns in Figure 3-25 describe different conditions: The left column shows
the scheduler load as seen from Connection Acceptance Control (CAC). New connec-
tions are accepted as long as their guaranteed rates fit the spare bandwidth of the
scheduler. The center column shows the case in which all Queues 2..10 are filled; that
is, all non-real-time connections are sending data. The total non-real-time bandwidth, in-
cluding the spare bandwidth, is then distributed to the 9 queues according to their weight.
In this case, two weight factors are defined. Queue 6 has weight of 1, others have weight
of 10. The right column shows the case of only three queues (6, 7 and 9) filled; all other
connections are not sending data at this time. Again, the available bandwidth is fairly dis-
tributed among the queues, still conserving the 1:10 ratio defined by their weights.
Notice that bandwidth of the real-time connections is not affected by bandwidth re-ad-
justments; but, remains constant over time under the assumption that real-time
connections are constantly sending data. If, however, a real-time connection should not
use its bandwidth, the bandwidth would be used immediately by the non-real-time con-
nections. The behavior of the WFQ scheduler shown in Figure 3-25 for non-real-time
connections has advantages for both the network operator and for the end user:
• The available bandwidth is always used completely, resulting in optimum usage of
transmission resources.
• A user paying for a higher guaranteed rate also obtains higher throughput under all
load conditions.
Data Sheet
85
2001-12-17